http://ncix.com/products/?sku=49865&...nufacture=ASUS
only 2 ports but the price is right, plus usb3.
SATA expansion cards generally come in the form of raid cards, and are expensive.
You can try one of the syba cards:
http://ncix.com/products/?sku=53815&...nufacture=Syba
http://ncix.com/products/?sku=50773&...nufacture=Syba
I wouldn't trust the syba card enough to use its raid capabilities though.
If you'll be doing something that requires good HD speeds accross multiple drives stay away from the Syba cards. They are pci-e v1 1x (250MB/s) which can be easily maxed out by 2 decent drives.